题目

16. You cannot be too careful. Which of the following sentences doesn’t have the same meaning of the underlined sentence? _____ A. You cannot be careful at all. B. You cannot be over careful. C. You cannot be careful enough. D. You cannot take enough care. 答案：C已知函数.（Ⅰ）当时，求函数的极小值；（Ⅱ）当时，过坐标原点作曲线的切线，设切点为，求实数的值；（Ⅲ）设定义在上的函数在点处的切线方程为： ，当时，若在内恒成立，则称为函数的“转点”.当时，试问函数是否存在“转点”.若存在，请求出“转点”的横坐标，若不存在，请说明理由.